This disclosure is based upon, and claims priority from French Application No. 99/02125, filed on Feb. 19, 1999 and International Application No. PCT/FR00/00285, filed Feb. 7, 2000, which was published on Aug. 24, 2000 in a language other than English, the contents of which are incorporated herein by reference.
The invention relates to a method for producing scratchable blocks on a support and a support incorporating such a block.
Scratchable blocks means any pattern printed on a support for the purpose of being removed simply by scratching with a nail or any object of sufficient hardness, the objective generally being to discover an inscription or a design printed underneath the said block.
Up to the present time use has been made of screen printing or heat transfer printing technologies for producing the scratchable blocks.
In both cases, the material used for the printing has good covering power and sufficient adhesion with respect to the support in order not to come off by itself, but insufficient adhesion to be able to resist scratching.
However, such technologies are not particularly well suited to mass production because of their low speed of deposition and/or the complexity of use.
However, there are greater and greater moves towards the use en masse of such scratchable blocks, naturally in the field already known, which is the field of games such as lotteries and disposable cards.
The applicant is also moving towards other uses, for example all applications involving portable supports such as smart cards (banking smart cards and/or electronic purses and/or telephone smart cards).
In such applications, the scratchable block could be used for covering for example a number useful to the user.
The existing printing technologies for depositing scratchable layers or scratchable blocks of materials on supports made of paper pulp such as paper or cardboard which exist today, that is to say heat transfer or screen printing methods, are not at all adapted to the problem of productivity, as stated, because of their low speed of deposition and/or their complexity of use.
In addition, the production of more elaborate scratchable blocks, that is to say for example multicolour or multishape, is here also a restrictive element in the technologies currently being used.
The object of the invention is a method for resolving the problems of speed and dynamic change of size, shape and colour of the scratchable block in the context of an industrial or other use.
The object of the invention is therefore more particularly a method for producing scratchable blocks on a support, principally characterised in that it includes the use of a technique of ink-jet printing.
According to another characteristic of the invention, the ink used is an ink of the phase change type (hot melt, in English terminology).
According to another characteristic, the inks used contain oligomers and polyamides.
According to another characteristic of the invention, the support on which deposits of scratchable blocks can be effected may be a plastic support such as an integrated circuit card (smart card) whatever the standard of the card and whatever the application.
The ink used contains the ester of a hydrogenated abietic acid (a tackifier) and a plasticiser. In the case of printing on a plastic support, the amount of hydrogenated abietic acid ester in the composition of the ink amounts to 16.5% to 27% and that of the plasticiser will respectively be 15% to 4.5%.
According to another characteristic of the invention, the support can be made from rigid paper pulp (cardboard) or flexible paper pulp (paper).
According to another characteristic of the invention, the printing by ink jet is obtained by means of one or more print heads controlled according to the shape, size and/or colour of the block to be produced.
According to another characteristic, the print heads used are of the piezoelectric type.
Another object of the invention is a support containing information or a graphic on one face and a scratchable block masking the said information or graphic. It is characterised in that the said scratchable block is composed of juxtaposed and/or superimposed dots of material.